The present invention relates to a vinyl chloride polymer composition prepared by blending a copolymer which prepared by firstly graft-polymerization methyl methacrylate as a main compohent onto a styrene-butadiene rubber, and then, onto the obtained copolymer, secondly graft-polymerizing styrene as a main component (hereinafter referred to as "MBS resin") prepared under the particular condition with vinyl chloride polymer; the polymer composition being capable of giving a molded article having excellent transparency and impact-resistance as well as excellent resistance to various solvents.
It has been known that vinyl chloride polymer has excellent solvent-resistance, low and transparency in comparison with other widley use resin but has poor impact-resistance.
In order to improve the impact-resistance, MBS resin has been developed and vinyl chloride polymer blended with MBS resin is widely employed for food packing, beauty kit, and the like.
As above, in case that MBS resin is employed, the impact-resistance in a molded article of vinyl chloride polymer can be improved, but excellent transparency or whitening property in bending which vinyl chloride polymer, per se, possesses tends to lower by adding MBS resin. Therefore, when MBS resin is employed in practical use, it is the most important problem how is the impact-resistance increased while minimizing the lowering of the above properties and there has been carried out various studies. However, in case that MBS resin is practically employed, it is practical that a suitable kind of MBS resin is selected and employed depening upon the properties to be desired into vinyl chloride polymer.
The impact-resistance in a molded article of vinyl chloride polymer can be improved by employing a vinyl chlorde polymer to which MBS resin is added (hereinafter referred to as "reinforced vinyl chloride polymer"). In case that the molded article is a casing, the casing is filled with edible oil such as corn oil or olive oil and a stress is applied more powerful to the casing in the course of transport or storage, the impact-resistance remarkably lowers, and in the extreme case, there might be little difference in impact-resistance between vinyl chloride polymer to which MBS resin is not added and the reinforced vinyl chloride polymer.
In the instant specification, "impact-resistance is excellent" means that the property of maintaining the strength is excellent under the above condition.
That is to say, it cannot be recognized that the correlation exists between the case that MBS resin can improve the impact-resistance in a molded article of vinyl chloride polymer when, as is generally employed, the above-mentioned stress is not applied to vinyl chloride polymer, and the case that MBS resin can retain the impact-resistance in a molded article of vinyl chloride polymer when the above-mentioned stress is applied to the vinyl chloride polymer.
Therefore, it is proposed in Japanese Examined Patent Publication (Tokkyo Kokoku) No. 18621/1974 that a particularly prepared MBS resin is suitable for use in which solvent-resistance is required.
In Japanese Examined Patent Publication No. 18621/1974, there is disclosed that MBS resin is prepared by firstly graft-polymerizing monomers including styrene as a main component onto a butadiene rubber including a proportion of particles having a particle size of not less than 0.15 .mu.m (1500 .ANG.) being not less than 50% (% by weight, hereinafter referred to as "%") and that having a particle size of not more than 0.1.mu. (1000 .ANG.) being not more than 15%, and then thereonto graft-polymerizing methyl methacrylate. According to the above-mentioned technique, the solvent-resistance is improved in comparison with the case employing a conventional MBS resin, but still it is unsatisfactory.
As above, in order to obtain MBS resin which can give excellent solvent-resistance into the molded article of vinyl chloride polymer, it is assumed that different technique or technical combination from the means of preparing a usual MBS resin is necessay.
An object of the invention is to provide a vinyl chloride polymer composition capable of giving a molded article having excellent solvent-resistance, transparency and impact-resistance.